1. Field of the Invention
The present invention relates to a video display device and a light guide module which can be applied to the same.
2. Description of the Background Art
U.S. Pat. No. 4,572,163 (Patent Document 1) discloses a projection display device. In the projection display device, outgoing light from a xenon lamp is condensed, passing through an opening of a light shielding plate, and enters an input opening of a rod integrator.
The light shielding plate is fixed on a support mount, standing in front of the rod integrator, and the opening thereof is so provided as to face the input opening of the rod integrator. With this structure, necessary light enters the rod integrator while unnecessary light is reflected on the light shielding plate toward the xenon lamp. The opening of the light shielding plate is configured to be larger than the input opening of the rod integrator.
The light entering the rod integrator is repeatedly reflected on an inner surface of the rod integrator and goes out from an output opening thereof as light which is rectangularly transformed to have improved uniformity. The light outgoing from the rod integrator goes through a lens, a mirror, a prism, and the like, and is modulated by a display device such as a DMD (Digital Micromirror Device) or the like and projected on a screen as video light.
In general, by forming the opening of the light shielding plate and the input opening of the rod integrator as rectangles with the same aspect ratio (in other words, as similar rectangles), it is possible to cause the light passing through the light shielding plate to enter the rod integrator with high efficiency.
Further, by forming the input opening and the output opening of the rod integrator to have the same aspect ratio as that of a pixel area of the display device, it is possible to use illumination light in the display device without any waste and therefore display a bright video image on the screen.
Pixel areas of display devices, however, have various aspect ratios, such as well-known 4:3 and 16:9. For this reason, in the structure of the above-discussed background art, for the display device with the aspect ratio of 4:3, it is necessary to provide a rod integrator having an input opening and an output opening with the aspect ratio of 4:3 and a light shielding plate having an opening with the aspect ratio of 4:3 while for the display device with the aspect ratio of 16:9, it is necessary to provide a rod integrator having an input opening and an output opening with the aspect ratio of 16:9 and a light shielding plate having an opening with the aspect ratio of 16:9.
Further, there is sometimes a case where even display devices having the same aspect ratio have pixel areas of different sizes. For this reason, it is necessary to prepare a rod integrator and a light shielding plate for each size of pixel area.
Specifically, in the structure of the above-discussed background art, it is necessary to provide both a rod integrator and a light shielding plate as exclusive ones in accordance with the aspect ratio and the size of a pixel area of a display device. In other words, the rod integrator and the light shielding plate can be used only as a particular one-to-one combination.